1. Field of the Invention
The present invention concerns a filter module for a frequency converter comprising a filter circuit housed in a casing for connection to said converter.
2. Description of the Prior Art
Frequency converters for supplying power to three-phase asynchronous motors essentially comprise a rectifier (AC-DC converter) which supplies a DC voltage to a smoothing or filter capacitor and an inverter (DC-AC converter) using power transistors or thyristors and energized by said filtered DC voltage.
The rectifier is a rectifier bridge connected to a single-phase or three-phase AC line voltage.
The inverter is connected to the phase windings of the motor. It generates a three-phase variable voltage and frequency power supply from the DC voltage supplied by the rectifier.
The transistors are operated in pulse width modulation (PWM) mode to generate a waveform as close as possible to a sine wave.
In many operating environments it is necessary to add to the frequency converter one or more of the following five types of filters:
an input filter to limit the propagation of radio-frequency interference on the mains power supply; PA1 an input filter to limit low-frequency harmonics of the AC line voltage frequency generated by the converter; PA1 an input filter to enhance the immunity of the converter to AC line voltage surges; PA1 an output filter to limit propagation of radio-frequency conducted electromagnetic interference in the motor power supply cable; PA1 output filter to limit voltage surges and sudden radio-frequency fluctuations at the motor terminals.